Bill Bedford - Mousa.biz - has a number of etched sides leaving you to do quite a bit of work, but these are available now unlike many of the other offerings, that rely on a lucky strike on an auction site or the bottom of a traders box of bits at an exhibition.

I am not sure if they are in the current list but D&S did produce kits for several of the Parker GC London extension stock. They have been seen on Ebay but he may still do batches possibly for the GC Society.

Old type, short, Triang / Hornby clerestories with alterations to details of sides, ends and bogies, plus new underframe fittings and new roofs, masquerading (fairly effectively I hope) as Edwardian GC non-corridor / suburban stock. A cheap way to start and to practice some modelling skills if you happen to have suitable access to some of these old coaches. A better result than I achieved is possible if you also replace the bogies with proper Fox ones, rather than just disguise the Mk1 bogies, and if you narrow down the bodies, but that's rather more work:

Jidenco / Falcon Brass parts, with modifications and a lot of bits from other sources or home-made, built up into GC Barnum coaches. Not the place to start unless you really like a challenge and can see it through to a worthwhile standard - otherwise you may just be wasting your time, your money, and using up parts that could have found better uses:

In neither case are these the kind of thing I'd have time to repeat these days - other modelling tasks and the wider demands of life fill my time.

Most subjects, models and techniques covered in this thread are now listed in various categories on page1

Dec. 2018: Almost all images that disappeared from my own thread following loss of free remote hosting are now restored.

I drew up some sides for a few of the clerestory carriages, the intention being that they're grafted onto the old Triang/ Hornby clerestory bodies. So far I've done a brake third and an all third and I have plans to do one or two more- a lavatory composite and I think maybe a brake composite too- but they're a project for another time. I'd be happy to give you copies of the drawing files for the two types I have done though, if you like?

Like Atlantic I've got a few re-roofed Hornby clerestories and they do look quite convincing.

If you can find some, the Grafar mainline and suburban carriages also look quite GCR-ish. I've done a rake of each and with a suitable repaint and the matchboarding drawn on they rather look the part for the later Robinson-designed stock.

~Addendum~

If you can find them, the old Triang Caley coaches can also be cut down and turned into respectable facsimilies of the post-Parker, pre-Robinson 50' mainline stock of the early Edwardian period. Here are a few I built last year.

Resurrecting this thread a bit I have some Bill Bedford GCR coaches to build, notably 3A7, 3L4, 3Q2, and 3B5. I was wondering if anyone can tell me what bogies these would have been fitted with and if there are any publications which would give some details of these vehicles (especially as they would have appeared 1912/1913)?